1. Field of the Invention
The present invention relates to a lever mechanism in a sewing machine driving device and more particularly to an improvement of a lever mechanism interlocked with a pedal in a sewing machine driving device.
2. Description of the Prior Art
Heretofore, clutch motors have widely been used for driving sewing machines, particularly industrial sewing machines, in which the clutch brake is operated on and off by means of a mechanical lever. Industrial sewing machines provided with such type of a motor are constructed as shown in FIG. 1, in which a sewing machine body 12 is mounted on the upper surface of a sewing machine table 10, while to the lower surface of the table 10 is fixed a clutch motor 14 provided with a control unit 16. To the casing of the control unit 16 is attached a lever 22 which is pivotable about a lever pin 24. The lever 22 is connected to a pedal 20 through a connecting rod 18. To an intermediate portion of the lever 22 is attached a tension spring 26, whereby the lever 22 is pivotally urged in a clockwise direction at all times. Further, a compression spring 27 is attached to the fore end of the lever 22, whereby a counterclockwise pivoting force is imparted to the lever 22. The position of the lever 22 is assumed to be N when the pedal is in a neutral state.
Depression and kick back of the pedal 20 actuate the lever 22 through the connecting rod 18, and the control unit 16 operates in accordance with the movement of the lever 22. More particularly, when the pedal 20 is depressed from the neutral position N to position A and then returned to the neutral position N, the sewing machine stops operating in a lowered position of its needle, that is, with the needle penetrating the cloth.
Next, if the pedal 20 is kicked back from position N conversely to position B, only the cloth presser rises (the cloth becomes rotatable) while the neddle is held in its lowered position. If the pedal 20 is depressed from position B again to N.fwdarw.A position, it becomes possible to effect a high-speed sewing by means of the sewing machine body 12. On the other hand, according to another sequence, if the pedal 20 is further kicked back to position C, the needle of the sewing machine body 12 will go up and stop in its raised position (in which the needle is off the cloth), and subsequently the thread cutting operation is completed. If the pedal is operated to N.fwdarw.C position at a time, the operation in the intermediate B position will not be performed.
Thus, on the kick-back side of the pedal 20 there are two positions, i.e., B and C positions, and therefore the compression spring 28 actually comprises a spring mechanism using two compression springs which are arranged side by side. More particularly, only one compression spring is compressed between N.fwdarw.B positions, while both compression springs are compressed between B.fwdarw.C positions, whereby a clear difference is given in the touch of pedal opeation between N.fwdarw.B and B.fwdarw.C positions.
Such conventional lever mechanism has been disadvantageous in that it requires a large number of components of the spring mechanism between N.fwdarw.B.fwdarw.C positions and is expensive and in that the adjustment of spring pressure must be done through two special bolts. Consequently, the number of parts is increased, the structure becomes complicated and the adjustment of the spring mechanism cannot be done easily.